Transient Pseudohypoparathyroidism as a Cause of Late-onset Hypocalcemia in Neonates and Infants

Abstract

Transient pseudohypoparathyroidism is a rare cause of late-onset hypocalcemia in neonates and infants. The purpose of this study was to investigate the clinical presentation and natural course of transient pseudohypoparathyroidism in neonates and infants. Methods: From 1995 to 2006, 21 patients under 3 months of age were admitted to our department because of late-onset neonatal hypocalcemia. Among these, five were noted to have transient hypocalcemia, hyper-phosphatemia and elevated serum parathyroid hormone levels. Their clinical data, biochemical findings and natural course were thoroughly analyzed. Results: All five patients were boys with increased neuromuscular irritability as their initial clinical manifestation. Initial biochemical data showed calcium 1.5 ± 0.16 mmol/L, phosphorus 9.6 ± 1.5 mg/dL, intact parathyroid hormone 182 ± 93 pg/mL and tubular reabsorption of phosphorus 94.8 ± 3.7%. Two of the patients had magnesium deficiency. After reduction of phosphorus intake and supplementation with calcium and/or magnesium as indicated, the biochemical derangements resolved in 28 ± 3 days. Conclusion: Neuromuscular irritability is usually the initial clinical presentation of transient pseudohypoparathyroidism. Aside from delayed renal maturation, pseudohypoparathyroidism is also caused by magnesium deficiency. Such a disturbance usually resolves before 3 months of age.

Keywords

• hyperphosphatemia
• hypocalcemia
• magnesium deficiency
• pediatrics
• pseudohypoparathyroidism